1. FIELD OF THE INVENTION
The present invention relates to a wire ribbon used for a deflection yoke coil mounted in a television receiver, a display unit, and the like.
2. DESCRIPTION OF THE RELEVANT ART
With the recent development of high-vision television receivers and high-definition display units, the specifications associated with color mismatching, i.e., misconvergence, of the cathode-ray tube screens of these apparatuses tend to be stricter. With this tendency, it is earnestly desired that a deflection magnetic field be controlled more precisely.
A deflection yoke mounted in the cathode-ray tube of a television receiver or a display unit is designed such that horizontal deflection coils are wound on the top and bottom sides of a bobbin as a funnel-shaped winding frame along its inner surface, and a vertical deflection coil and a core are wound around the bobbin.
FIG. 1 shows an example of a bobbin for a saddle type deflection coil used for a general deflection yoke. A plurality of coil-winding grooves 5 are formed in this bobbin 2. For example, coiling wires 11 shown in FIG. 2 are wound in layers along these coil-winding grooves 5, thus forming a deflection coil. As the coiling wire 11, a conductive wire (including a litz wire) coated with an insulating layer 4 is used.
In winding the coiling wires 11 along the coil-winding groove 5, if the coiling wires 11 are not bound, conductive wires are wound in layers one by one or several wires at a time by an automatic winding machine, thus forming a deflection coil.
Owing to variations in the stretching force acting on the coiling wires 11 as they are wound and other reasons, the coiling wires 11 are displaced and biased as shown in FIG. 2, or the order of winding of the coiling wires 11 is altered and hence such winding as previously designated by a design instruction cannot be practiced. Furthermore, since the biased states of the coiling wires 11 of deflection coils that are mass-produced differ from one another for each product, a deflection field cannot be regulated with high precision. In addition, mass-produced products vary in quality, and hence the yield decreases. Therefore, this conventional winding method is disadvantageous in terms of cost. Even in the conventional winding method, as the width of the coil-winding groove is reduced, the displacement and bias of each coiling wire 11 are reduced to satisfy the original design. In this case, however, a ratio L/R between an inductance L and a resistance R is reduced, resulting in a deterioration in coil performance.
In order to solve the above problems, the applicant of the present invention has previously proposed a deflection coil formed by using wire ribbons, each constituted by a plurality of conductive wires bound to be arranged parallel in a row as shown in FIG. 3, instead of using single conductive coil wires one by one as in the prior art.
A wire ribbon 15 is formed as follows. As shown in FIG. 3, a plurality of single-core wires, each having an insulating layer 4 and a hot-melt adhesive layer 9 formed on the surface of a conductive wire 8 consisting of copper, aluminum, or the like, are arranged parallel in a row and are bonded to each other so as to be integrated into the wire ribbon 15.
Since the single-core wires of the wire ribbon 15 are orderly fixed within the wire ribbon 15, the single-core wires are not shifted within the wire ribbon 15, or the order of the wires is not altered. Therefore, by winding these wire ribbons 15 in layers along the coil-winding groove 5, a deflection coil can be manufactured, which is free from the above-described problem of the great displacement of each single-core wire.
When the wire ribbons 15 are wound in layers along the coil-winding groove 5 to form coil layers, and the coil layers are to be bonded to each other, the wire ribbons are energized and heated while the coil layers are pressed by a pressurizing jig 20, as shown in FIG. 4. With this operation, the hot-melt layers of the respective coil layers are melted and bonded to each other. However, since the width of the coil-winding groove 5 is set with a margin with respect to the width of the wire ribbon 15 so as to allow the wire ribbon 15 to be smoothly inserted, upper and lower wire ribbons may be wound to be displaced from each other. In such a case, when the hot-melt layers are melted by energizing and heating while the wire ribbons 15 are pressed, part of the pressing force acting on the single-core wire 14 of the upper layer is obliquely applied to a displaced single-core wire 14a of the lower layer. As a result, the single-core wire 14a of the lower layer is separated and moved toward a gap 12 between the coil-winding groove 5 and the wire ribbon 15. For example, as shown in FIG. 5, a single-core wire 14b of the upper layer enters a gap 12a between single-core wires 14a and 14a' of the lower layer. As a result, the wire ribbons 15 may be bonded and solidified in a deformed state, e.g., a distorted or biased state.